请参考以下教程

我希望这对你有帮助，但在你必须阅读NSError的文档

这是我最近发现的一个非常有趣的链接

这有点超出了问题范围，但如果你没有NSError选项，你可以总是显示低级别错误:

 NSLog(@"Error = %@ ",[NSString stringWithUTF8String:strerror(errno)]);

extension NSError {
    static func defaultError() -> NSError {
        return NSError(domain: "com.app.error.domain", code: 0, userInfo: [NSLocalizedDescriptionKey: "Something went wrong."])
    }
}

我可以使用NSError.defaultError()每当我没有有效的错误对象。

let error = NSError.defaultError()
print(error.localizedDescription) //Something went wrong.

我将尝试总结Alex的伟大回答和jlmendezbonini的观点，添加一个修改，使所有内容都与ARC兼容(到目前为止，它不是因为ARC会抱怨，因为你应该返回id，这意味着“任何对象”，但BOOL不是对象类型)。

- (BOOL) endWorldHunger:(id)largeAmountsOfMonies error:(NSError**)error {
    // begin feeding the world's children...
    // it's all going well until....
    if (ohNoImOutOfMonies) {
        // sad, we can't solve world hunger, but we can let people know what went wrong!
        // init dictionary to be used to populate error object
        NSMutableDictionary* details = [NSMutableDictionary dictionary];
        [details setValue:@"ran out of money" forKey:NSLocalizedDescriptionKey];
        // populate the error object with the details
        if (error != NULL) {
             // populate the error object with the details
             *error = [NSError errorWithDomain:@"world" code:200 userInfo:details];
        }
        // we couldn't feed the world's children...return nil..sniffle...sniffle
        return NO;
    }
    // wohoo! We fed the world's children. The world is now in lots of debt. But who cares? 
    return YES;
}

现在，我们不再检查方法调用的返回值，而是检查error是否仍然为nil。如果不是，我们就有麻烦了。

// initialize NSError object
NSError* error = nil;
// try to feed the world
BOOL success = [self endWorldHunger:smallAmountsOfMonies error:&error];
if (!success) {
   // inspect error
   NSLog(@"%@", [error localizedDescription]);
}
// otherwise the world has been fed. Wow, your code must rock.

请参考以下教程

我希望这对你有帮助，但在你必须阅读NSError的文档

这是我最近发现的一个非常有趣的链接

答得好，亚历克斯。一个潜在的问题是NULL解引用。Apple关于创建和返回NSError对象的参考

...
[details setValue:@"ran out of money" forKey:NSLocalizedDescriptionKey];

if (error != NULL) {
    // populate the error object with the details
    *error = [NSError errorWithDomain:@"world" code:200 userInfo:details];
}
// we couldn't feed the world's children...return nil..sniffle...sniffle
return nil;
...